Storm water runoff collected from roof areas and paved areas were historically simply allowed to collect in municipal storm water drainage systems and transferred to a body of water. However, more recently, the preferred handling of storm water runoff is to direct it into soil, and such handling is required by building codes in many cases. The traditional construction of storm water handling systems has been concrete tanks or infiltration trenches filled with large gravel or crushed stone with perforated pipes running therethrough.
Molded chamber structures are increasingly taking the place of concrete structures for use in leaching fields or to gather storm water runoff. Molded chamber structures provide a number of distinct advantages over traditional concrete tanks. For example, concrete tanks are extremely heavy requiring heavy construction equipment to put them in place. In leaching fields and storm water collection systems, the gravel used in constructing them is difficult to work with and expensive. It also tends to settle and reduces the overall volume of the trench by as much as 75%. Stone-filled trench systems are expensive and inefficient since the stone occupies a substantial volume, limiting the ability of the system to handle large surge volumes of water associated with heavy storms. Both the stone and the perforated pipe are also susceptible to clogging by particles or debris carried by water.
Molded plastic chamber structures have been introduced in the market for handling storm water. U.S. Pat. No. 5,087,151 to DiTullio, the disclosure of which is hereby incorporated by reference, discloses a drainage and leaching field system comprising vacuum-molded polyethylene chambers that are designed to be connected and locked together in an end-to-end fashion.
Such chambers typically have an arch-shaped cross-section and are relatively long with open bottoms for dispersing water to the ground. These chambers may be laid on a gravel bed side-by-side in parallel rows to create large drainage systems. End portions of the chambers may be connected to a catch basin, typically through a pipe network, in order to efficiently distribute high velocity storm water. The chambers are typically positioned in a trench on top of a bed of materials that facilitates the flow of fluid into the earth.
However, such chambers become increasingly more difficult to manufacture and handle the larger they are designed. Consequently, the volume of liquids that can be accommodated by drainage chambers is limited by the ability to manufacture and ship them.
It would be desirable if molded plastic structures could be used in larger volume applications, where the benefits of ease of installation and cost savings could be available.